Power system



Oct. 25, 1.932. E. M. JOHNSON ET AL. 1,383,929

POWER SYSTEM Filed Nov. 13. 1929 FIG.

f INVENTORS E-M-JOHNSON AND H-c-mEQsoN- BY l %!M ATTORNEY Patented Oct. 25, 1932 "UNITED STATES PATIENT OFFICE ERIC MAURICE JOHNSON, OF BROOKLANDS, AND HENRY GAJ'ETAN PIEBSON, OF HALE,

ENGLAND, ASSIGNOBS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING CO!- iANY, A CORPORATION OF PENNSYLVANIA rowan svsrnu Application fled November 18, 1829, Serial No. 406,871, and in Great Britain November 15, 1988.

This invention relates to power systems of the kind in which a prime mover such as a reciprocating steam engine if utilized to operate a main drive and is assisted by a second -prime mover, as for example a steam turbine using the exhaust steam of the first mentloned engine. Power systems of this kind have been proposed for the propulsion of sh1ps,both the reciprocating engine and the turbine being coupled to the main drive or propeller shaft, the engine directly and the turbine through suitable gearing.

An ob'ect of the invention is to render the speed of the second prime mover independent of the speed of the main drive so that it may be used to drive auxiliary apparatus at a substantially constant speed. An additional advantage of the invention is that the efliciency of operation of the second prime mover is improved in cases where this consists of a turbine or other engine whereof the elficiency decreases considerably below certain speeds. According to the invention a power system of the kind set forth is provided wherem the second prime mover is coupled to the main drive by variable power transmission means and-is also required to supply power for driving an auxiliary load, and governor means is provided responsive to the speed of said secaoond prime mover, and adapted to vary the ratio of said power transmission means so as to decrease the load thereon due to the main drive when the-speed tends to decrease below a predetermined limit. The same or a second governor may further be provided adapted to increase the supply of motive fluid to the second prime mover when the speed thereof tends to fall below a predetermined limit and the load thereon due to the main drive has been reduced by variation of the power transmission ratio to a predetermined extent. The variable power transmissionmeans may comprise a direct current electric gen erator arranged to be driven by the second prime mover and connected electrically to a direct current propulsion motor operatively associated with the main drive, the governor means foe-varying the load on the second I prime mover being arranged to vary the re- Po sistance of the generator field windings in order to keep the speed of the generator andsecond prime mover substantially constant when the speed of the lattentends to vary, for example'due to variations in the supply of exhaust steam coming from the first prime mover.

v The second prime mover preferabl comprisesa steam turbine adapted to recelve the exhaust steam from the first prime mover and also arranged to receive steam from another source.v A mixed pressure turbine may advantageously be employed for this purpose, the high pressure portion bein normally inoperative, but bein brought into action when the su ply of ex aust steam to the turbine is insu cient to maintain the speed thereof above a predetermined value and the load thereon due to the main drive has already been reduced a predetermined amount by variation of the power transmission ratio.

The speed at which the second prime mover and any auxiliary machine connected thereto is driven may thus be maintained substantially constant at all times irrespective of variations-in the speed of the main drive or the quantity of motive fluid exhausted from the first prime mover. If the auxiliaryload upon the second prime mover comprises an auxiliarygenerator a supply of electric power at a constant voltage may be obtained.

The invention is illustrated in the accompanying drawing, wherein:

Fig. 1 is a diagrammatic representation of a marine installation arranged according to the invention; and,

Fig. 2 is a diagram illustrating an electrical governing arrangement thatmaybe employed in carrying out the invention.

Referring more particularly to Fig. 1, a

first prime mover 1', represented as a triple expansion reciprocating engine is coupled to a main shaft 2 for driving a propeller 3, and is adapted to deliver its exhaust steam to the low pressure section 4' of a mixed pressure turbine 4, which in turn exhausts to acondenser 5. A bypass 6 and a valve 7 are provided, whereby, when desired, the supply of exhaust steam from the engine 1 may be shut ofi from the turbine and delivered directly t9 the condenser 5. The turbine 4 is also provided with 'a high section 8 adafted rom to receive live steam through a pipe 9 a suitable source, which in the example shown 1 is constituted by the main steam supply to the engine 1. The turbine 4 drives a direct current generator 10 which is adapted to deliverelectrical energy to a direct current motor 11 connected with the shaft of the propeller 3. An. auxiliary generator 12 is also adapted to be driven by the turbine 4 and supplies electrical energy for various purposes on boar the ship, including the excitation of the generator 10 and the motor 11. A switch 13 is provided for reversing the electrical connections of the field windin s of the motor 11 and generator 10 and varia le resistances 14, 15

are also inserted in the field winding of the generator; 10. Suitable circuit breakers and such likeauxiliary devices incidental to the convenient operation of the arrangement may be provided in the circuits, as will be readily ation of the governor valve 17 and rheostat 15 in the desired manner is rovided.

One suitable form of mec anism for carrying out the necessary coaction between the governor 16, the rheostat 15, and the governor valve 17 is'illustrated by way of example in it controls.

Fig. 1 ofthe accompanying drawing, this mechanism being employed in conjunction with an oil relay operated governor system, which is a well known manner of associating a centrifugal governor with the devices which The rheostat 15 is shown as of the cylindrical type in which the resistance in circuit may be progressively increased or decreased by movement of an arm. 20 over a plurality of contacts 21. The valve 17 [is adapted tobe opened and closed by raising and lowering, a spindle 22. An oil relay 23 is provided and arranged to be controlled in well known manner by a pilot valve 23 connected to the governor 16 so as to im art up or down motion to a rod 24 each time the governor speed tends to decrease below or to rise above fpredetermined limits. 7

In Fig. 1 t e parts are shown at about the mid position. Falling speed of the turbine causes the governor 16 to admit oil to relay 23in such a way as to raise the rod 24. In the example given, the motion of-the rod 24 is imparted to the rheostat arm 20 by a pin 25 and to the governor valve through a pin 26, bell cranks 27 and 28 rotatable on dle an arm 33 and a link 34, all suitably situated in regard to the 0 rating parts. The bell crank 27 is provi ed at one end with a stop 32 ada ted, when the crank 27 has d the link 34, pivoted to the ends of the arm 33 and the bell crank 28 and results in the valve s indle 22 being raised to open the valve 1 The latter is opened against the action of a spring 22, so that in the event of the bell crank 27 being rotated in a counter-clockwise direction the spring will cause the valve operating mechanism and the valve itself to follow up the movement of the stop 32. The rollers or pins 25, 26 and 31 may be adjustably mounted in order to provide for adjustment between the various parts of the mechanism.

The plant is adapted to operate as follows: 1

Assume the plant to be working at full power and the governor valve 17 closed, the propeller shaft 2 is then driven directly by the engine 1 and the turbine is driven entirely by the exhaust steam delivered to the turbine section 4', the power of which is utilized to supply electric energy in both the propulsion system 10, 11 and the auxiliary system of the generator 12. If now, any reduction in the speedjof the reciprocating engine is made, there will result a diminished supply of exhaust steam to the turbine, the speed of which will fall.

The governor 16 responds to the fall in speed and controls the relay 23 to eiiect operation thereof raising the rod 24, so im arting clock-wise rotation to the bell cran s 20 and 27 The rotation of the crank 20 will result in the insertion of a greater amount of resistance 15 in the field circuit of the generator 10, but as yet the stop 32 will remain out of en agement with the arm 33. This reduction in output is continued until the load on the turbine is such that with the steam quantity then available, the desired constant speed of the turbine is substantially maintained. At this point, the governor 16 for the time being comes to rest.

Any su uent reduction in exhaust steam quantity resu ts in the repetition of the above process until finally the output of the generator 10 is reduced to zero. The quantity of exhaust steam then available is employed solely for the purpose of maintaining the out at of the auxiliary generator 12.

It will be appreciated that, so long as the motor 11 is excited and rotating, the out at of the generator 10 will be zero, not w en its field is zero, but when its generatedelecfixed shafts 29 and 30, a pin 31 on the spintro-motive force is insuflicient to circulate current around the circuit comprising its own armature, that of the motor 11 and also the interconnecting cables and switch gear. A reduction of the excitation of the generator .10 below the point in question will result in electrical energy being supplied from the motor 11, acting as a generator, to the gen-' erator 10, acting as a motor. The latter will, therefore, add its motive power to that of the turbine 4 to drive the auxiliary generator 12, at the required speed. This will continue under the control of the governor 16 until the combined power so obtained is insufficient to maintain the required speed.

At or about this point, the stop 32 engages the arm 33. Any further rise of the rod 24, due to the action" of the governor 16 in response to further decrease in the turbine speed, now produces acorresponding rise of the spindle 22, through the clock-wise rotation of the bell cranks 27 and 28 and movegoverning systems that numerous modifications of the control'system described above may be employed in effecting the governing action in accordance with the present invention.

The control system described above enables a substantially constant speed of the turbogenerator set to be maintained so that the. voltage. of the auxiliary generator 12 may also remain substantially constant. This latter effect may be produced by the use of an electrical governor in place of a centrifugal governor, for example by an arrangement such as illustrated in Fig. 2.

In Fig. 2, we show an electrical form of governing mechanism, which acts in response to the voltage of the auxiliary ge'n-.

erator 12 to maintain the same substantially constant. A coil is connected to the leads of the generator 12 and exerts a magnetic pull upwardly on a plunger 46 in opposition to the force of a spring 47. The plunger 46 is connected to the relay 23. which operates the variable resistance 15 and the valve 17 in the same manner as in the embodiment first described.

, Upon a decrease in the voltage developed by the generator 12, the plunger 46 moves downwardly under force of the spring 47.

The relay 23 is controlledto move the rod 24 upwardly, similarly to a decrease in speed in the embodimentshown in Fig. 1, for first turbine being controlled by the the conventional. manner.

decreasing the load on the turbine and then I -rod 24 downwardly to effect reverse operationas will be readily understood.

It will be appreciated that the arrangements above described permit of reversing the direction of rotation of the main engine 1 and the propeller 3, theelectrioal connections of the motor 11 and the generator 10 being reversed by the switch 13. Also when the main engine 1 is not working the turbine mav be supplied with live steam by the pipe 9 for the pur ose of supplying auxiliary electric power by thegenerator 12, the circuits of the generator 10 and motor 11 being suitably disconnected and the speed of the governor in From the foregoing it will be apparent that the invention provides a power system' of the kind referred to in which substantial? ly constant speed of the second prime mover or turbine is maintained by governor means which adjusts the load on one of two generators in accordance with the available supply' of exhaust steam for operating said prime mover, and when the load of, that generator is reduced substantially to zero and the supply of exhaust steam no longer suffices for the load of the second generator, 1

admits an appropriate amount of live steam to the prime mover so as to maintain the speed, and incidentally the output voltage of the second generator.

It is preferable, when applying the invention to practice'to make provision for uncoupling the main engine 1 from the propeller shaft and for rendering inoperative the means for relieving the turbine of propulsion load. A disengageable coupling 52 may be provided for this purpose. The turbine may then be used alone in an emergency to drive the propeller, with the main engine out of action. In such event the turbine would be supplied with steam entirely by pipe'9 and the admission of steam may be controlled by the governor or governors associated with valve 17 within the fully open and fully closed positions of said valve.

While in the above description an. electrical form of variable power transmission means between the second prime mover and the main drive has been described, it will be evident that the invention is not limited in this respect, but tha't'other forms of variable power transmission means may be employed.

,VVhile we have shown our invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modand also supplying power for'an auxiliary load, and governing means for maintaining thespeed of the second prime mover substantially constant comprising means responsive to the speed of the second prime mover for varying the power transmitted by said power transmission means so as to vary the load thereon due to the main drive.

2. In a power system, the combination of a first prime mover Coupled to a main drive, a second prime mover coupled to the main drive by variable power transmission means comprising an electric generator driven by the second prime mover and an electric motor operatively-associated with the mam drive andelectrieally connected to the generator,

said. second prime mover also supplyingpower for an auxiliaryload, and governing means for maintaining the speed of the second prime mover substantially constant compris- 1 ing-means responsive to the speed of the second prime moverfoljva'ryiiig the power transmitted by said power-transm1ss1on means so as'to'varythe load thereon due to the main drive.

3. In a power system, the combination of a rime mover, means for supplying motive fluid from a variable source to said prime 1 mover, means for supplying'motive fluid to 10 prime mover normally receiving only the mosaid prime mover from a second source, said tive fluid from said variable source, a driven machinewc'onnected to the prime mover and driven thereby,cmeans for applying .additional'load to theprime mover and for varying said load in fesponse'to the s ed thereof to maintain the same substantia y constant,

' and means for admitting motive fluid from said second sourcewhen the supply from the variable source is insuflicient to maintain the speed of the'turbine.

4. The combination with a prime mover receiving a variable quantity of motive fluid and drivin" adirect current generator and a driven mac ine, of means for governing the speed of the prime mover comprisin means for varyin the load on the generator y varying the fie excitation current of the generator in' response to the speed of "the prime mover. m

i 5. Thpgeombination with a prime mover receiving'f -a variable quantity of motive, fluid and driving an electric generator and a driven machine, of means for governing the speed of-the prime mover comprising means for varying the load on the generator by varying the generator field strength in response to the speed of the'prime mover.

6. In a power system the combination of a first prime mover coupled to a main drive, a

second rime mover coupled to the main drive by variable power transmission'means comprisin an e ectric generator driven by the secon prime mover and an electric motor operatively associated with the main drive and electrically connected to the generator, said second rime mover receiving the exhaust from tlie first prime mover, means including and controlled by a regulating valve forv supplying other motive fluid to the second prime mover, and means for governing the speed of the second prime mover compr sin a governor responsive to the speed thereo means controlled by the governor for varying the strength of the generator field, and connecting means between the governor and the regulating valve including a lost motion connection, said governing mechanism operating, upon decrease in speed, to decrease the strength of the generator field and to take up the lost motion in said lost motion connection, and, upon further decrease in speed after said lost motion is taken up, to open the regulating valve through said I 0st motion connection. a a

' 7. Ina power system, the combination of a prime mover receivinga variable quantity of motive fluid, said prime mover being coupled to a main drive b variable power transmis sion means and a I o supplying power for an auxiliary load, and overning means for maintainin the speecf of the prime mover substantially constant comprising means responsive to the speed ofthe prime-mover for varying the power transmitted by said power transmission means so;as to vary the load 5 thereon due to the main drive.

. In testimony whereof, we have hereunto subscribed our names.

ERIC MAURICE JOHNSON. HENRY OAJETAN PIERSON. 

